The ultimate objective of the project is to increase the reliability of wind turbine blades through the development of proof-testing techniques, which will both identify developing problems before they become critical and improve the understanding of damage processes. The proof-testing techniques will be developed during a series of static and fatigue tests on small and commercial scale blades and demonstrated on an in-service turbine. Acoustic emission (AE) will be used as the primary non-destructive test method, backed up by a combination of acousto-ultrasonics (AU), fibre optic (FO) strain sensing, and infra red thermography (IRT). Real-time monitoring of these tests will contribute further to the understanding of failure processes in the blades and form the basis for feeding back information to designers for optimisation of the design and manufacturing processes. The intermediate objectives are:

1. reliable, real-time, non-destructive damage characterisation during full scale laboratory testing of wind turbine blades by means of acoustic emission (i.e. the identification of threshold levels of activity or particular signal characteristics which can be directly related to the extent and type of damage in the structure),
2. definition of acoustic emission and acousto-ultrasonic proof test procedures and quantifiable evaluation criteria (acceptance / rejection) during static and fatigue testing of wind turbine blades,
3. demonstration of structural integrity assessment of an in-service blade by direct on-site proof testing.

The technical/scientific targets of the project include reliable quantification of fatigue damage growth in real time, improved understanding of fatigue processes, and the development of procedures for the validation of design against fatigue. From the acoustic emission point of view, it is expected that the project team will upgrade or develop new techniques and methodologies for source characterisation, location, and noise discrimination. Unsupervised pattern recognition (UPR) techniques will be developed for the signal processing of acoustic emission measurements and integrated into a software package for the monitoring of certification tests. This software will constitute a major deliverable of the project. Over the medium term the following benefits can be expected:

1. improved certification procedures for static and/or fatigue full scale testing,
2. cost saving through optimised design (material/weight saving),
3. cost saving through failure prevention (machine availability and replacement cost).

Selected Consortium Papers

• Acoustic emission monitoring for wind turbine blades undergoing static and fatigue testing, Proceedings of 15th World Conference on Non-Destructive Testing, Roma, October 2000   (PDF: 187kB, 7 pages)

• Acoustic Emission Monitoring During Certification Testing Of Wind Turbine Blades, Proceeding of the 2001 European Wind Energy Conference, Copenhagen, July 2001   (PDF: 110kB, 4 pages)

• Acoustic Emission Monitoring of Small Wind Turbine Blades, AIAA_2002_0063, Proceeding of the 21st ASME Wind Energy Symposium, Reno, USA, 14-17, January 2002   (PDF: 394kB, 11 pages)

• Damage Classification of Acoustic Emission using Aegis Pattern Recognition Software from Ten Small Wind Turbine Blade Tests, Proceeding of Global Windpower, Paris, April 2002   (PDF: 278kB, 5 pages)

• Real-time evaluation of wind turbine blades with acoustic emission monitoring during certification tests, NDT.net, NDT.net - Special Issue on Acoustic Emission, September 2002, Vol. 7 No.09  

• Structural integrity evaluation of wind turbine blades using pattern recognition analysis on acoustic emission data, The 25th European Conference on Acoustic Emission Testing - EWGAE 2002, Prague, Czech Republic, 11–13 September 2002   (PDF: 176kB, 8 pages)

• P.A. Joosse, M.J. Blanch, A.G. Dutton, D. Kouroussis, T.P. Philippidis, P. Vionis, Acoustic Emission Monitoring of Small Wind Turbine Blades, JSEE Paper No. 10/2-112, Vol. 124, pp 446-454, November 2002.  (Abstract only PDF: 63kB, 1 page)

• A G Dutton, M J Blanch, P Vionis, D Lekou, D R V van Delft, P A Joosse, A Anastassopoulos, D Kouroussis, T Kossivas, T. P. Philippidis, T. T. Assimakopoulou, G Fernando, C Doyle, A Proust, Acoustic Emission Condition Monitoring Of Wind Turbine Rotor Blades: Laboratory Certification Testing To Large Scale In-Service Deployment   (PDF: 472kB, 11 pages)

• D. J. Lekou, P. Vionis, P. A. Joosse, D. R. V. van Delft, D. Kouroussis, A. Anastasopoulos, M. J. Blanch, A. G. Dutton, A. Proust, Full-Scale Blade Testing Enhanced by Acoustic Emission Monitoring, 2003 European Wind Energy Conference, Madrid  (PDF: 59kB, 7 pages)

• M.J.Blanch and A.G.Dutton, Acoustic Emission Monitoring of Field Tests of an operating Wind Turbine, Damage Assessment of Structures, Proceedings of the 5th International Conference on Damage Assessment of Structures (DAMAS 2003), Southampton , UK, 1-3 July 2003  (PDF: 616kB, 5 pages)

Project Partners (Number, Name, Contact & Key Functions of the Partner)

1. STFC Rutherford Appleton Laboratory (RAL) - Geoff Dutton
   Project coordination and wind turbine testing laboratory
   https://www.eru.rl.ac.uk
2. Centre for Renewable Energy Sources, Wind Energy Department (CRES) - Pantelis Vionis, Denja Lekou
   Wind turbine blade testing laboratory and research
   http://www.cres.gr
3. Delft University of Technology, Civil Engineering and Geosciences, Stevin II laboratory (DUT) - Don van Delft, Peter Joosse
   Note : Dutch blade testing work is now (2007) carried out at a new facility: https://www.tudelft.nl/en/
4. Envirocoustics (ENVAC) - Nassos Anastasopoulos, Dimitrios Kouroussis
   Acoustic Emission and Ultrasonic testing services
   http://www.acoustic-emission.com
5. Geobiologiki (GEOB) - Theodore Kossivas
   Wind turbine blade manufacturer
   Note: Theodore Kossivas is now working for the company Compblades
6. University of Patras, Department of Mechanical Engineering and Aeronautics,
   Section of Applied Mechanics (UPAT) - Theodore P Philippidis
   Wind turbine blade design and materials characterisation
7. Cranfield University, Engineering Systems Department, Royal Military College of Science, Shrivenham,
   Sensors and Composites Research Group (UCRAN) - Gerard F Fernando, Crispin Doyle
   Fibre optic sensor research, development and manufature
   http://www.rmcs.cranfield.ac.uk/senscomp
8. Euro Physical Acoustics S.A. (EPA) - Alain Proust
   Acoustic Emission and Ultrasonic testing services